Neural prosthesis

ABSTRACT

A neural prosthesis includes a centralized device that can provide power, data, and clock signals to one or more individual neural prosthesis subsystems. Each subsystem may include a number of individually addressable, programmable modules that can be dynamically allocated or shared among neural prosthetic networks to achieve complex, coordinated functions or to operate in autonomous groups.

RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 13/550,231, filed Jul. 16, 2012, which is a continuation ofU.S. patent application Ser. No. 11/842,929, filed on Aug. 21, 2007,which is a divisional of U.S. patent application Ser. No. 10/272,484,filed on Oct. 16, 2002 (now U.S. Pat. No. 7,260,436), which is anon-provisional of U.S. Provisional Patent Application No. 60/329,721,filed on Oct. 16, 2001. This application incorporates theabove-identified applications herein by reference in their entirety andclaims priority to all aforementioned applications for all purposes.

BACKGROUND OF THE INVENTION

Neurological trauma, dysfunction or disease can leave persons withsevere and life threatening motor or sensory disabilities that cancompromise the ability to control basic vital functions. Persons withneurological impairments often rely on personal assistants, adaptiveequipment and environmental modifications to facilitate their dailyactivities. Neural prostheses are highly effective methods for restoringfunction to individuals with neurological deficits by electricallymanipulating the peripheral or central nervous systems. By passing smallelectrical currents through a nerve, neural prostheses can initiateaction potentials that eventually trigger the release of chemicalneurotransmitters to affect an end organ or another neuron. Techniquesexist to selectively activate axons of any size or location within anerve or fascicle, making it possible to preferentially target smallsensory fibers or duplicate natural motor unit recruitment order tominimize fatigue and grade the strength of a stimulated muscularcontraction. In addition to exciting the nervous system, the propercurrent waveform and configuration of electrodes can block nerveconduction and inhibit action potential transmission. Thus, in principleany end organ normally under neural control is a candidate for neuralprosthetic control.

Neural prosthetic devices that electrically stimulate paralyzed musclesprovide functional enhancements for individuals with spinal cord injuryand stroke such as standing and stepping, reaching and grasping, andbladder and bowel function. Current implanted neural prosthetic systemsutilize considerable external powering and signal processing, and eachsystem is tailored to the specific application for which it wasintended. The need to design a customized implant system for eachapplication severely limits progress in the field and delaysintroduction of new technology to the end user.

Generally, neural prostheses consists of both external and implantedcomponents. External components consist of sensing apparatus, signalprocessing, and transmission to an internal implanted component. Theinternal component receives the externally transmitted signal andgenerates appropriate stimuli in response to the signal. The internalcomponents might also include sensors, which measure some internalvariable and transmit the signal to the external apparatus forprocessing.

Implanted neural prostheses have been successfully applied to thesensory (e.g., cochlear and visual prostheses) and motor (i.e. handgrasp) systems, as well as to the viscera (e.g., micturition,defecation) and central nervous system (e.g., deep brain stimulation).

In further advancements of neural prostheses, a number of sensors andactuators have been combined into networks that cooperate to extend aneural prosthesis over an area of the body, with nodes of the networkoperating under control of a central controller. Such networks aredescribed, for example, in U.S. Pat. No. 5,167,229 to Peckham, et al.

It is clear that neural prosthetic approaches can provide boththerapeutic and functional benefits to individuals with impairments dueto neurological injury or disorder. However, as a significantdisadvantage prior neural prostheses typically provide only crudenetworking capability and limited, if any, programmability at nodeswithin the prosthetic network. Despite the promise of neural prostheses,there remains a need for a an architecture that is sufficiently open andflexible to permit the implementation of complex and varying prostheticfunctions, and to invite the design of a wide range of sensors andactuators for use therewith.

SUMMARY OF THE INVENTION

A neural prosthesis may include a centralized device that can providepower, data, and clock signals to one or more individual neuralprosthesis subsystems. Each subsystem may include a number ofindividually selectable, programmable modules that can be dynamicallyallocated or shared among neural prosthetic networks to achieve complex,coordinated functions or to operate in autonomous groups.

In one aspect, the invention is an implantable system including aplurality of modules implantable in living tissue, each module includingat least one of a sensor or an actuator, a processor, and a networkinterface configured to communicate with at least one other one of theplurality of modules; and a power source providing a data signal, and apower signal to each one of the plurality of modules, each moduleobtaining power from the power signal.

The power source may further provide a clock signal. The clock signalmay be a variable system clock signal modulated onto the power signalfor controlling power consumption by one or more of the plurality ofmodules. The nervous system may include at least one of sensory nerves,motor nerves, and neural circuits.

The data signal may include control information for at least one of theplurality of modules. The data signal may be addressable to one or moreselected ones of the plurality of modules. One of the plurality ofmodules may modulate a data signal onto the power signal.

In another aspect the invention is a system including a first neuralprosthesis controlling a nervous system in a first region of a body, asecond neural prosthesis controlling the nervous system in a secondregion of the body; and a controller connected in a communicatingrelationship with the first neural prosthesis and the second neuralprosthesis, the controller coordinating a transfer of data between thefirst neural prosthesis and the second neural prosthesis to achieve abody function that combines the first region of the body and the secondregion of the body.

The communicating relationship may include a data network having a datatransmission rate of at least 100 kbps. The communicating relationshipmay include a wireless network. The body function may include walking.The body function may include a muscle contraction in the first regionin response to a user-initiated movement detected in the second region.

The system may include one or more additional neural prostheses. The oneor more additional neural prostheses may be connected in a communicatingrelationship with the controller, or with the first neural prosthesis orthe second neural prosthesis.

In another aspect, the invention is a system including a power supplypackaged for implantation into a cavity of a body, the power supplyincluding a rechargeable power source, a port configured to couple therechargeable source to a charger that is external to the body cavity,and control circuitry, the control circuitry configured to generate apower signal from the rechargeable power source, the power signal beinga charge-balanced signal, the control circuitry further configured tomodulate a clock signal onto the power signal, and to modulate a datasignal onto the power signal, thereby providing a modulated powersignal; and a plurality of leads extending from the power supply andcarrying the modulated power signal, the leads being biocompatible leadsadapted for connection to one or more power draining devices.

The plurality of leads may include a pair of leads for each limb of thebody that contains power draining devices, each plurality of leadscarrying a different modulated power signal. The port may include aradio frequency transcutaneous link for coupling to the charger. Therechargeable source of direct current may include a battery. The batterymay be at least one of a nickel cadmium battery, a lithium ion battery,and a nickel-metal hydride battery. The power supply may include a 500mW power supply.

The system may further include a controller that controls operation ofthe power supply and a communication link for maintaining communicationsbetween the controller and an external device. The controller maydownload programming information through the communication link. Theprogramming information may control operation of the power supply. Theprogramming information may control operation of a device connected toone or more of the plurality of leads. The communication link transmitsat least one of test information and diagnostic information between thecontroller and the external device. The communication link may transmitsensor data to the external device. The communication link may transmita user input to the controller.

In another aspect, the invention is device including at least one of asensor or an actuator, a processor, a network interface coupled to theprocessor and the at least one of a sensor or an actuator, the networkinterface adapted for connection to a network, and including circuitryto receive power from a power signal provided over the network, and todemodulate a clock signal and a data signal from the power signal, and ahousing that encloses at least a portion of the at least one sensor oractuator, the network interface, and the processor, the housing formedof a biocompatible material, and shaped and sized for implantation intoa body.

The network interface may modulate a data signal onto the power signal.The processor may be at least one of a microprocessor, amicrocontroller, or a programmable digital signal processor. The networkinterface may maintain communications using at least one of the CANprotocol or the MICS protocol. The sensor or actuator may include asensor selected from the group consisting of an electroencephalogramsensor, an electromyogram sensor, an electrooculogram sensor, anelectroneurogram sensor, and a three-dimensional accelerometer. Thesensor or actuator may include a sensor for sensing at least one ofpressure, finger contact, joint angle, limb segment velocity, ortemperature. The sensor or actuator may include an actuator includes anactuator selected from the group consisting of a nerve stimulator, ablocking cuff-electrode nerve stimulator, and drug delivery device.

In another aspect, the invention is a device including a first networkinterface connected in a communicating relationship with a first neuralprosthetic that autonomously controls a nervous system of a first regionof a body, the first network interface configured to provide a firstpower signal, a first data signal, and a first clock signal to the firstneural prosthetic; a second network interface connected in acommunicating relationship with a second neural prosthetic thatautonomously controls the nervous system of a second region of the body,the second network interface configured to provide a second powersignal, a second data signal, and a second clock signal to the secondneural prosthetic; a controller that selectively passes data from thefirst neural prosthetic to the second neural prosthetic; and a housingthat encloses at least a portion of the first network interface, thesecond network interface, and the controller, the housing formed of abiocompatible material and shaped for implantation into a body.

The controller may selectively pass data from the second neuralprosthetic to the first neural prosthetic. The data signal may bemodulated onto the power signal. The clock signal may be modulated ontothe power signal. The network interface may employ a wired communicationmedium. The network interface may employ a wireless communicationmedium. The controller may generate control information to coordinatebody function in each of the first neural prosthetic and the secondneural prosthetic. The device may further include one or more additionalneural prosthetic networks.

In another aspect, the invention is a system including a plurality ofdevices, each one of the plurality of devices being a biocompatible,implantable device that shares a communication medium, the plurality ofdevices grouped into one or more networks across the communicationmedium wherein devices in a network operate autonomously to control abody function; and a controller that dynamically reallocates one or moreof the devices among the one or more networks to perform a differentbody function.

The controller may be a programmable controller coupled to thecommunication medium. The controller may be distributed amongprogrammable processors operating on each one of the plurality ofdevices. More than one of the networks may share one of the plurality ofdevices. The communication medium may include at least two branches thatare physically separated from one another by a bridge. At least one ofthe networks includes a device from each of two or more of the at leasttwo branches, control data within the at least one of the networks beingcommunicated through the bridge.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is pointed out with particularity in the appended claims.The advantages of the invention may be better understood by referring tothe following description taken in conjunction with the accompanyingdrawing in which:

FIG. 1 is a block diagram of a neural prosthesis;

FIG. 2A is a block diagram of an actuator module that may be used in aneural prosthesis;

FIG. 2B is a block diagram of a sensor module that may be used in aneural prosthesis;

FIG. 3 shows a neural prosthesis implanted in a user;

FIG. 4 is a block diagram of a bridge that may be used in a networkedneural prosthesis;

FIG. 5 is a block diagram of a data structure for communicating data ina neural prosthesis;

FIG. 6 shows a neural prosthesis for legs; and

FIG. 7 depicts control of the neural prosthesis of FIG. 6.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

To provide an overall understanding of the invention, certainillustrative embodiments will now be described, including neuralprostheses deployed for therapeutic use in humans. However, it will beunderstood that the methods and systems described herein can be suitablyadapted to other applications and environments where control ormonitoring of a nervous system, either human or non-human, may beusefully employed. All such variations are intended to fall within thescope of the invention described below.

In the following description, corresponding reference charactersindicate corresponding components throughout the several views of thedrawings, unless specifically indicated otherwise.

FIG. 1 is a block diagram of a neural prosthesis. The neural prosthesis100 includes a communication medium 102 and a number of modules 104. Themodules 104 may include sensors and/or actuators, and may be implantedin any distributed fashion throughout a body. Although four modules 104are shown in FIG. 1, the neural prosthesis 100 may include more or fewermodules 104.

Each module 104 may be linked to the communication medium 102, which maybe, for example, any electrically conductive material, such as a copperwire encased in a biocompatible rubber or plastic insulator, or aplurality of leads encased as a cable in a coaxial, twisted pair, orribbon configuration. The communication medium 102 may distribute apower signal, a clock signal, and a data signal to the modules 104,either through one physical network or through a number of coextensivephysical networks.

In one embodiment, power is distributed with an alternating currentsignal, which may reduce tissue damage as well as corrosion of metalcomponents in a biological environment. The clock signal and the datasignal may be modulated onto the alternating current power signal usingany suitable modulation scheme. For example, clock data may be conveyedin a frequency of the power signal, and data may be modulated onto theclock/power signal using amplitude shift keying. Currently popularprotocols that may be used for communicating data in a neural prosthesisinclude variations of Ethernet, Universal Serial Bus (“USB”), andFirewire.

In another embodiment, the communication medium 102 may include wiredand wireless portions. For example, the power signal and a clock signalmay be distributed through a wired portion of the communication medium102, using a clock signal modulated onto an alternating current powersignal as described above. The data signal may be wirelesslycommunicated using any suitable short-range wireless communicationssystem that propagates signals using radio frequency or otherelectro-magnetic carriers. One example of such a protocol is the MedicalImplant Communication Service (“MICS”), a recently FCC approved systemfor wireless communications into or out of a body in a medicalenvironment. Any other standard or proprietary wireless system suitablefor use with the devices described herein may similarly be employed. Thedata signal may instead be distributed using any ultrasonic carrierfrequency, such as a one-hundred kilohertz sonic signal, or othertechniques employing mechanically transmitted energy. The data signalmay also be distributed using a Personal Area Network (“PAN”) in whichthe human body is used as a conductor to capacitively couple smallcurrents among network elements.

In another embodiment, the communication medium 102 may be entirelywireless, with each module 104 supplying its own power through a batteryor other rechargeable or renewable power source. Power-up and power-downsignals, as well as a controllable system clock, may be transmittedthroughout the wireless communication medium 102 to permit powermanagement within the neural prosthesis 100, and portions thereof, inthe absence of power distribution through the wired communication medium102.

One network protocol that may be usefully deployed in the neuralprosthesis 100 is the Controller Area Network (“CAN”) protocol. This isan ISO standard (ISO 11898) for serial communications, originallydeveloped for networking automobile components, and more recentlyfinding broad application in industrial automation and control systems.The protocol defines the physical layer and the data-link layer of theOpen Systems Interconnection (“OSI”) Reference Model, and provides forarbitration and error handling in a peer network that shares a physicalcommunication medium. A number of microcontrollers have been designedspecifically for use with the CAN protocol, and may be usefully deployedwith the neural prosthesis 100 described herein, such as Atmel'sT89C51CC01/02 microcontrollers. High-level protocols (e.g, applicationprotocols) have been designed specifically for use with the CAN protocolto address matters such as start-up behavior, flow control, and statusreporting within the CAN-based network. In one embodiment of the neuralprosthesis, the physical layer and data link layer used with thecommunication medium 102 are defined by the CAN protocol with acommunication rate of 100 kilobits per second (“kbps”).

FIG. 2A is a block diagram of an actuator module that may be used in aneural prosthesis. The module 200, which may be one of the modules 104of FIG. 1, may include a network input/output 205, galvanic isolationunit 210, a local network interface 215, a data modulator/demodulator220, an AC/DC conversion unit 225, a power conditioning unit 230, anetwork controller 235, a remote programming unit 240, an external resetunit 245, a microcontroller 250, an output-stage power conditioner 255,one or more output stages 260, a waveform template 265, and one or moreoutputs 270. It will be appreciated in the following discussion that,while described separately, certain of the above components may beintegrated into a single semiconductor device or chipset. It willsimilarly be appreciated that certain of the components may instead berealized as discrete analog and digital circuitry. All such realizationsare intended to fall within the scope of the systems described herein.

The network input/output 205 physically connects the module 200 to apower/data network, such as the communication medium 102 of FIG. 1. Thismay be any tap or plug connector, preferably one that seals theconnection from surrounding tissue and/or body fluids when implanted.

The galvanic isolation unit 210 may serve to physically isolateelectronics within the module 200 from the network (not shown) to whichthe module 200 is connected. The galvanic isolation unit 210 mayinclude, for example, a transformer for inductively coupling electricalsignals within and without the module 200. In addition to decoupling ofelectro-magnetic noise generated by the module 200 from the network,isolation may be used as a safety feature in biological instrumentationsystems to prevent accidental leakage of power or other signals into thebiological medium.

The local network interface 215 may include circuitry to detect andrecover a clock signal and a data signal from a signal received throughthe input/output 205. The local network interface 215 may be abi-directional interface capable of receiving or transmitting a datasignal. The data demodulator/modulator 220 may operate on a physicalsignal to add or remove data using, for example, amplitude shift keyingor any other modulation scheme capable of sharing the network with aclock signal. The clock signal may be obtained directly from the datacarrier, or may derived from the data carrier signal using, for example,a phase-locked loop or other frequency control circuitry. In certainwireless embodiments of the systems described herein, the module 200 mayinclude clock generation circuitry such as oscillators and/or othertuned circuits to independently generate local clock signals.

The network controller 235 may implement any communications protocolsuitable for a neural prosthesis. The network controller 235 may residephysically on the same semiconductor device as a microcontroller where,for example, a commonly used protocol has microcontrollers builtspecifically to implement the protocol. For example,commercially-available microcontrollers such as Atmel's T89C51CC01/02fully implement the physical layer and data link layer of CAN. This andother widely-used protocols may also be realized in digital signalprocessors, processors, and microcontrollers. Optionally, these or othernetwork protocols may be realized using other semiconductor integrationtechnologies such as custom-designed Application Specific IntegratedCircuits, with or without additional programmability or applicationlogic, and other programmable devices such as Programmable Gate Arraysor Programmable Logic Devices. Any such realization of the networkcontroller 235 is intended to fall within the scope of the descriptionprovided herein.

The Alternating Current/Direct Current (“AC/DC”) conversion unit 225begins a power signal path within the module 200, as distinct from thedata signal and clock signals demodulated therefrom. The AC/DCconversion unit 225 rectifies an alternating current signal receivedfrom the network into a direct current. The power conditioning unit 230further conditions the signal to remove ripples in the direct currentsignal and regulate the voltage such that it is suitable for use withthe analog and digital circuits and devices of the module 200. The AC/DCconversion unit 225 and the power conditioning 230 may be combined intoa single circuit or semiconductor device, and may include any step-up orstep-down conversion stages suitable for conforming the external networksignal into an internal DC power signal for the module 200.

The microcontroller 250 may be any programmable device or devicessuitable for controlling the neural prostheses, and may include one ormore microcontrollers, microprocessors, application specific integratedcircuits, programmable digital signal processors, programmable gatearrays, and/or programmable logic devices, as well as external volatileand/or non-volatile memory to support the operation thereof, such asRandom Access Memory (“RAM”), Read-Only Memory (“ROM”), ProgrammableRead-Only Memory (“PROM”), Electrically Erasable Programmable Read-OnlyMemory (“EEPROM”), flash memory and so forth. Thus, the term“microcontroller” as depicted in FIG. 2A and described herein should beunderstood to include a number of devices capable of performing thefunctions described below. In certain embodiments, such as Atmel'sT89C51CC01, the network controller 235 and programmable flash memoryreside on the microcontroller chip as well. In general, themicrocontroller 250 may have power consumption characteristicsconsistent with power supplies available in the network, and processingpower adequate to receive and execute programming for use in a neuralprosthesis.

A remote programming unit 240, which may be realized as a boot loader orother executable code on the microcontroller 250, detects program orfirmware updates for the microcontroller 250 and manages reprogrammingof the microcontroller 250 with the updated code. Updates may beincremental, involving replacement of a specified block or blocks ofcode stored in the microcontroller 250, or may include complete removalof all current code and replacement with new code received from thenetwork. This capability may be employed, for example, to updatewaveforms that are stored in the waveform template 265. The remoteprogramming unit 240 may also, or instead, permit reconfiguration of themodule 200 and redeployment of the module 200 in a new or modifiedneural prosthetic network.

The external reset detector 245 provides for remote activation andde-activation of the module 200. A reset signal may be transmitted tothe module 200 through any external stimulus, such as a fixed magnetplaced near the module 200. While any type of signal may be used,including electrical signaling, magnetic signaling, or electro-magneticsignaling, or physical switching, the signal is preferably providingthrough some medium that is non-invasive, and does not require properoperation of any remaining components of the module 200.

The output-stage power conditioner 255 may be coupled to the powerconditioning unit 230, and may include any circuitry for AC/DCconversion, DC/AC conversion, voltage step-up, voltage step-down,filtering, frequency modification, or any other signal conditioningrequired for operation of the outputs 270. Many actuators, for example,operate with thirty to forty Volts of DC power, which may require asignificant step-up in voltage from the AC signal used on the network,as well as the DC power provided for other components within the module200, which may operate in a range of, for example, three to five Volts.

The output stages 260 may provide further signal conditioning for one ormore output signals to the outputs 270. This may include, for example,combining the power signal from the output-stage power conditioning unit255 with one or more output waveforms from the waveform template 265.This may also include protection and isolation circuitry to protect aphysical system that receives signals from the outputs 270, and toprotect the internal circuitry of the module 200 from electricaltransients in the physical system.

The waveform template 265 may reside in a volatile or non-volatilememory, either within the microcontroller 250 or external to themicrocontroller 250. The waveform template 265 may operate, for example,as a look-up table of waveforms that may be applied by themicrocontroller 250 to the outputs 270. The waveform may also, orinstead, use linear and/or non-linear models to generate suitablewaveforms which may be triggered by a signal from the microcontroller250. The waveform template 265 may permit separation of program logicand actuator control. For example, program logic may dictate extensionof a leg with a “move” command, while actuator control to achieve thisresult may entail a complex and time-varying series of neural signalsand associated muscular contractions. As another example, certaineffects and muscle responses are achieved by blocking neural signalsthat might otherwise be present. In this environment, signals toactuators may be based on empirical data or theoretical modelsdescribing biological relationships. In any case, the shape, amplitude,and duration of pulses to achieve a desired response may be stored asone or more waveforms in the waveform template 265. This functionalseparation may also permit a neural prosthesis to have actuatorstailored to a particular recipient without any modification of theprogramming to achieve a gross effect, such as closing a hand.

The outputs 270 may include any actuators suitable for use in a neuralprosthesis. In one embodiment, this includes one or more electrodes thatmay output stimulus, such as drive pulses stored in the waveformtemplate 265. The outputs may stimulate nerve cells or some otherportion of the nervous system, which in turn initiate a musclecontraction or body function. Outputs 270 may include, for example,nerve stimulators, blocking cuff-electode nerve stimulators, or drugdelivery devices.

The module of FIG. 2A may be hermetically sealed or otherwise housed ina biocompatible material, except where network connections 205 oroutputs 270 require physical coupling to an external environment.

FIG. 2B is a block diagram of a sensor module that may be used in aneural prosthesis. Some of the components of the sensor module 280 maybe the same as, or similar to, the components of the actuator module 200described above. Thus it will be noted that the input/output 205, thegalvanic isolation unit 210, the local network interface 215, the datademodulator/modulator 220, and AC/DC conversion unit 225, the powerconditioning unit 230, the network controller 235, the remoteprogramming unit 240, and external reset detector 245, and themicrocontroller 250 may all be as described above with reference to FIG.2A. The sensor module 280 may further include a signal conditioning unit285, an input amplification unit 287, an amplification parameters unit289, and one or more inputs 295, all described in greater detail below.

The one or more inputs 295 may include any type of sensor that may beusefully employed in a neural prosthetic. This includes, for example,biopotential sensors, for electroencephalograms (“EEGs”), sensors forelectromyograms (“EMGs”), sensors for electrooculograms (“EOGs”),three-dimensional accelerometer(s) that measure body orientation andmotion, sensors for obtaining nerve recordings such as pressure orfinger contact, and sensors for detecting physical quantities associatedwith physiology such as joint angle (through a variety of differenttransducers), limb segment velocity, temperature, O₂ content, glucoselevels.

The input amplification unit 287 may serve to isolate an external mediumfrom the electronics of the sensor module 280. The input amplificationunit 287 may also perform various instrumentation functions, such asdifference amplification of an input signal, filtering, sampling, and soforth.

The signal conditioning unit 285 may convert a signal received from theinput amplification unit 287 (typically an analog signal) into a formsuitable for storage and processing by the microcontroller 250(typically a digital representation of the analog signal).

The amplification parameters unit 289 may store one or more parametersassociated with the inputs 295, including, for example, calibration datafor the inputs 295 or waveforms for use in matched filtering. Theamplification parameters unit 289 may permit separation of program logicfrom calibration of the inputs 295 and associated functions, asdescribed above with reference to the waveform template 265 of FIG. 2A.

Data gathered from the inputs 295, either in raw or processed form, maybe stored in a buffer, which may be associated with the networkcontroller 235 or the microcontroller 250, for transmission over thenetwork. This data may be transmit periodically according to a schedulestored on the sensor module 280, or may be provided upon an externalrequest for data received over the network.

In certain embodiments, one of the modules 104 of FIG. 1 may include oneor more sensors as well as one or more actuators, provided there is notexcessive interference between the signals of the two components.

FIG. 3 shows a neural prosthesis implanted in a user. The neuralprosthesis 100 may include a number of physically separatedcommunication mediums 102 or branches 102, each interconnecting one ormore modules 104. A bridge 302 may interconnect the branches 102 of theneural prosthesis 100. As described in more detail below, thisconfiguration may advantageously facilitate operation of autonomousnetworks along each branch 102, while permitting coordination offunction across branches 102, or communications between modules 104 ondifferent branches 102, all under control of the bridge 302. While ninemodules 104 and four branches 102 are shown in FIG. 3, it will beappreciated that the neural prosthesis 100 may accommodate more or lessbranches 102, and more or less modules 104.

It should also be appreciated that independent networks may be formedwithin the neural prosthesis 100. These networks may be formed alongbranches 102 that define the physical topology of the neural prosthesis100, or between and across branches 102 such that any two or moremodules 104 within the neural prosthesis 100 may be grouped into aseparate, virtual network to perform a desired function. It should alsobe appreciated, with reference to the programmability of the modules 104described above, that the virtual networks may be dynamicallyre-allocated and reconfigured according to a desired function of theneural prosthesis 100.

More generally, control may be exercised autonomously over variousregions of the body by defining a region and programming modules 104within the region to operate autonomously. For example, one neuralprosthetic network may be created for a left leg region, and another fora right leg region. Thus a complete neural prosthetic may be dynamicallycreated for each region to be controlled. These networks may alsocommunicate with one another through the communication medium 102 toachieve coordinated movements such as walking. Regions may instead bedefined along functional lines, such as bladder or bowel control. Itwill further be understood that regions of the body need not be mutuallyexclusive, and may include overlapping or concentric physical regionswithin the body, according to the desired function of each neuralprosthetic formed in this manner.

FIG. 4 is a block diagram of a bridge that may be used in a networkedneural prosthesis. The bridge 400, which may be the bridge 302 of FIG.3, may include battery recharge electronics 402, a radio frequency powerrecovery unit 404, a radio frequency wireless data link 406, a remoteprogramming unit 408, a power source 410, supervisory electronics 412, acontroller 414, an external reset detector 416, a DC/AC conversion unit418, a global data modulation unit 420, a global network controller 422,a global data demodulation unit 424, a number of distribution units426-432, and a number of external connectors 434-440. It will beappreciated that, while four external connectors 434-440 are shown, moreor less external connectors 434-440 may be used with a system asdescribed herein, according to the number of separate physical networksconnected to the bridge 400, and the expandability desired for thesystem.

The battery recharge electronics 402 receives power from the radiofrequency power recovery unit 404, or port, and converts the recovered(AC) power into a form suitable for recharging the power source 410. Theradio frequency power recover unit 404 may be a microstrip patch orantenna suitable for recovering power from a nearby, tunedradio-frequency source. The battery recharge electronics 402 may convertthe recovered power into a steady, DC voltage, or a stream of pulses orother signal suitable for recharging the power source 410. Thesupervisory electronics 412 may monitor the charging status of the powersource 410, and determine what recharging power should be delivered fromthe battery recharge electronics 402 to the power source 410. Thesupervisory electronics may implement safety features such as low poweralerts and overcharge prevention, as well as other features to improveefficiency of the power source 410, extend the life of the power source410, or otherwise manage power within the system.

The power source 410 may be, for example, a rechargeable power sourcethat delivers 500 mW of continuous power. This may include batteriessuch as a lithium-ion battery, a nickel cadmium battery, or anickel-metal hydride battery. The power source 410 may also include arenewable power source such as a fuel cell, and it will be appreciatedthat such a power technology will employ different supporting circuitryand physical apparatus than that depicted in FIG. 4.

The radio frequency wireless data link unit 406 may maintain a data linkbetween the bridge 400 and an external system. The external system may,for example, provide programming for modules 104 connected to the neuralprosthesis 100, or retrieve telemetry data from one or more sensormodules 200 connected to the neural prosthesis 100. While a radiofrequency data link 406 is depicted in FIG. 4, it will be appreciatedthat any data link may be used, including any of the wirelesscommunications techniques described above, as well as a percutaneousconnections.

The remote programming unit 408 may detect programming data receivedover the data link maintained by the radio frequency wireless data linkunit 406. As noted above, programming data may be for the bridge 400 orfor a module 104 connected to one of the external connectors 434-440.Where the programming data is for the bridge 400, the remote programmingunit 408 may manage loading of the programming data andre-initialization of the bridge 400. Where the programming data is forone or more of the modules 104, any transfer, loading, and execution ofthe programming data may be handled by the remote programming unit 408or the controller 414.

The controller 414 may maintain external communications with the neuralprosthesis 100, including the remote programming described above, aswell as routine inquiries to the neural prosthesis 100 for diagnosticsand data acquisition. The controller 414 may also communicate with thesupervisory electronics 412 to control recharging of the power source410, and to monitor a charge state of the power source 410. Thecontroller 414 may also manage power throughout the neural prosthesis100. For example, the controller 414 may generate power-up or power-downsignals to specific modules 104 within the neural prosthesis 100, or thecontroller 414 may reduce a system clock rate to one or more of theexternal connectors 434-440 in order to conserve power in one or morebranches 102 of the system that are in an idle or low activity state.

The controller 414 may also receive and process user inputs receivedthrough the wireless data-link 406, or through a separate percutaneousconnection to the controller 414. These user inputs may be convertedinto control signals that are distributed to modules 104 of the neuralprosthesis 100 through the external connectors 434-440.

The external reset detector 416 may receive an external reset signalthrough, for example, a wired connection to an external reset switch, orfrom a fixed magnet positioned near the external reset detector 416.When an external reset signal is received, the bridge 400 may be reset.Reset signals may also be transmitted over the branches 102 of theneural prosthesis 100 to all modules 104 connected thereto, or thesedevices may be reset through a separate, independent reset signal.

The DC/AC conversion unit 418 may convert the DC from the power source410 into an AC form, or other charge-balanced signal, suitable tooperate as a power signal for neural prosthesis 100. This AC signal maybe globally managed to increase or decrease the clock signal modulatedonto the AC signal. The clock signal may also be independently regulatedfor each branch 102 of the neural prosthesis 100 through thedistribution units 426-432.

The global data modulation unit 420 may operate to modulate data ontothe AC power signal provided by the DC/AC conversion unit 418. Theglobal data demodulation unit 424 may demodulate data received from thebranches 102 of the neural prosthesis, including, for example sensor andcontrol data from modules 104 connected to the branches 102.

The global network controller 422, receives control data from thecontroller 414, and identifies a branch 102 for transmission of thedata. This may include reprogramming data, requests for sensor data, orinstructions to one or more modules 104 connected to one or morebranches 102 of the neural prosthesis 100. The global network controller422 may also perform a filtering function. In operation, network trafficon each branch 102 of the neural prosthesis may be reduced by confiningtraffic for that branch 102 to that branch 102. However, where afunctional network of interoperating modules spans more than one branch102, the global network controller 422 may listen at each branch 102 fortraffic relating to the functional network and, where appropriate, passdata to one or more other branches 102. In this manner, operation of theneural prosthesis 100 may be coordinated across more than one branch 102of the neural prosthesis.

The distribution units 426-432 and the external connectors 434-440provide a physical interface to each branch 100 of the neural prosthesis100 which may function in a similar manner to, for example, theinput/output 205, galvanic isolation 210, and local network interface215 of one of the modules 200, 280 of FIGS. 2A and 2B. It will beappreciated that one significant difference is that the distributionunits 426-432 distribute power along a branch 102 of the neuralprosthesis, while the input stages of a module 200, 280 extract powerfrom the branch 102.

FIG. 5 is a block diagram of a data structure for communicating data ina neural prosthesis. The data structure 500 may include a start of frame502, an arbitration field 504, a control field 506, a data field 508, acyclic redundancy check field 510, an acknowledgement field 512, and anend of frame 514. This data structure 500 may be used to communicatebetween, for example, the controller 414 of the bridge 400 andindividual modules 104 of the neural prosthetic 100. The data structure500 also supports control and content specifiers that may be used tomaintain communication between modules 104 so that one or more groups ofmodules 104 may be formed into a self-managing network to perform adesired function. The data structure 500 may also support reprogrammingof one or more modules 104 through the communication medium 102 of theneural prosthetic 100.

The start of frame 502 includes one or more bits that signal thebeginning of a message for communication within the neural prosthetic.

The arbitration field 504 includes a priority of the message, andspecify a type of content for the message.

The control field 506 includes one or more bits that specify a length ofthe data field 508.

The data field 508 includes any data payload for communication withinthe neural prosthesis 100. This may include, for example, sensor datafrom a sensor module 200 in the neural prosthetic 100, actuator controldata for controlling an actuator module 280 in the neural prosthetic100, or programming data for programming a device 200, 280 in the neuralprosthetic 100.

The cyclic redundancy check (“CRC”) field 510 includes a CRC of data inthe message, and may be used for error checking for messagescommunicated through the neural prosthetic 100.

The acknowledgement field 512 includes one or more bits signaling anacknowledgement request, or a reply to an acknowledgement request sothat connection oriented messaging may be maintained among modules 104of the neural prosthetic 100.

The end of frame 514 includes one or more bits that signal the end ofthe message.

It will be noted that the data structure 500 described above correspondsto the message specification for the CAN protocol. While this datastructure is not dictated by the neural prosthetic 100 described herein,the data structure 500 does permit ready implementation withcommercially-available electronics. Module-to-module addressing is notexplicitly supported by the CAN protocol, which does not include adestination address. However, addressing may be effected within thebroadcast messaging of CAN by, for example, placing address informationwithin the data field 508, or by implying a destination module by themessage type specified in the arbitration field 504. In this manner,each module 104 may communicate with each other module 104 through theneural prosthetic network.

FIG. 6 shows a neural prosthesis for legs. The neural prosthesis 600includes an external user interface 610, a bridge 615, one or moreactuator modules 620, and one or more sensor modules 630-640. Arecipient 650 may have a left leg 660 with a left foot 665, a right leg670 with a right foot 675, and a torso 680. The prosthesis depicted inFIG. 6 may be used, for example, as an aid to a recipient 650 with lowerlimb paralysis. It will be appreciated that other arrangements,positioning, and combinations of modules may be used with a neuralprosthesis for legs, and that the following example does not limit thescope of the systems described herein.

The actuator modules 620 may be positioned, for example within paralyzedmuscles of the hips, the legs, and the ankles, as depicted generally inFIG. 6. Positioning of the actuator modules 620 may be refined for aparticular prosthesis recipient according to, for example, where theactuator modules 620 will achieve the greatest recruitment of sensorynerves, motor nerves, and neural circuits of the nervous system, andmuscles associated therewith. Positioning will also depend on whichmuscle groups will be used by the neural prosthesis 600.

A first sensor module 630 and a second sensor module 635 may beelectroneurogram (“ENG”) sensors that record nerve activity for the leftfoot 665 and the right foot 675 of the recipient 650.

A third sensor module 640 may include a three-dimensional accelerometeror other orientation sensor for monitoring orientation of the torso 680of the user 650.

The user interface 610 may be a wireless, hand-held device or any otherdevice suitable for communicating with the bridge 615 and receiving userinput from the recipient 650. The user interface may display statusinformation on a liquid crystal display, light-emitting diode display,or other display. Other status information, such as alarms, may besignaled through an audio output such as a speaker or a piezo-electricbuzzer. User input may be received through, for example, a joystick, akeypad, one or more individual buttons, a microphone coupled to voiceprocessing software, a touch pad, or any other input device. The userinput may be packaged as a wearable wireless device or a hand-heldwireless device. Any other packaging convenient to the recipient 650 mayalso be employed.

FIG. 7 depicts control of the neural prosthesis of FIG. 6. As depictedthe control system 700 permits a user to control a paralyzed musclesystem 702 through a user interface 704. The system may include ajoystick 706, a left leg sensor 708, a right leg sensor 710, a torsosensor 712, a user display 714, and an alarm 716. Processes executing onone or more modules 104 or a bridge 400 in the system may control statesof operation, including a system on/off process 718, a determine initialstate process 720, a menu process 722, a fall detection process 724, andone or more state control processes 726. The processes 718-726 maycontrol one or more states of the system, including a stand patternstate 730, a left leg step state 732, a right leg step state 734, a leftleg stair state 736, a right leg stair state 738 and an emergency fallstate 740. The states 730-740 generate drive signals for one or moreelectrodes 750, numbered as Electrode #1 through Electrode #n in FIG. 7.

The user interface 704 may include the joystick 706 through which a userenters commands, or any other data entry device, including, for example,keypads, touch pads, dials, knobs, buttons, a microphone (with voiceactivation and processing capability), a trigger, or any other inputdevice. The user interface 704 may also receive as input a signal from amodule 104 within the neural prosthesis 100. This may be, for example,neural signals from the left leg sensor 708, neural signals from theright leg sensor 710, or one or more torso orientation signals from thetorso sensor 712, which may be, for example, a three-dimensionalaccelerometer or other orientation sensor. Through these sensors708-712, a user may provide input to the system by intentional movementsof body parts where, for example a neural signal sensed at the left legsensor 708 may be detected and used as a trigger to begin a stepping orstair climbing motion. The inputs may also operate autonomously, i.e.,without conscious activation by a user. For example, the fall detectionprocess 724 may detect a potential fall based upon a change ininclination of the torso, and initiate an emergency fall process 740that overrides other processes. The emergency fall process 740 may, forexample, slowly relax leg muscles to permit the user to slowly collapseto the ground. The fall detection process 724 may also activate thealarm 716.

The system on/off process 718 is initiated by activation of an on/offswitch or other user input. The on/off process 718 may initializehardware and software in the neural prosthesis 100 and pass control tothe determine initial state process 720. The determine initial stateprocess 720 may, for example read sensor and state data from modules 104in the neural prosthesis 100 and determine an initial state for theneural prosthesis 100, as well as whether the user is in a safe positionto use the system 700.

The menu process 722 may drive the user display 714 to display one ormore options available to the user, among which the user may select, forexample, by operation of the joystick 706. The menu process 722 maypresent options such as, for the leg control prosthesis of FIG. 6,standing, stepping, or climbing stairs. Upon selection of a menu item,control may be passed to one or more state control processes 726 whichimpress electrode stimulus patterns 730-740 onto electrodes to obtainthe desired muscle activity.

Stimulus patterns 730-740 may be used in conjunction with sensor data.For example, where the nervous system responds to a foot touchingground, this signal may be detected and used to limit a stepping signaleven where the nervous system signal does not reach a user's brain.Stimulus patterns 730-740 may also be regulated by further user inputwhere, for example, a user may stop a stepping pattern through thejoystick when a desired leg position has been reached.

It will be appreciated that details of the system, such as sensorplacement, stimulus waveforms, and sequencing of actions may be highlydependent on an individual user's physiology and the desired motorfunction to be controlled. Specific stimulus patterns are thus notdescribed in detail here, however stimulus patterns for muscle movementsare well-characterized in the art, as shown for example in the followingreferences, the teachings of which are incorporated herein by reference:Kobetic R, Marsolais E B. Veterans Affairs Medical Center, Cleveland,Ohio. Synthesis of paraplegic gait with multichannel functionalneuromuscular stimulation. IEEE TRANSACTIONS ON REHABILITATIONENGINEERING (June 1994) 2; 2 (66-79); Popovic D, Stein R B, Ogurtoreli MN, Lebiedowska M, Jonic S. IEEE. Optimal control of walking withfunctional electrical stimulation: a computer stimulation study. IEEETRANSACTIONS ON REHABILITATION ENGINEERING (March 1999) 7; 1 (69-79);Skelly M M, Chizeck H J. Case Western Reserve University, Cleveland,Ohio, University of Washington, Seattle, Wash. Real-time gait eventdetection for paraplegic FES walking. IEEE TRANSACTIONS ONREHABILITATION ENGINEERING (March 2001) 9; 1 (59-68).

In the example system of FIG. 7, it is assumed, for example, that a userhas voluntary control over arms sufficient to operate a joystick. Ifthis were not the case, other user inputs could readily be adapted foruser input.

It will be appreciated that other options can be provided to the userthat are not described shown in FIG. 7. In each case, a stimulationpattern is developed and stored within the implanted neural prosthesis.In addition, there are other system parameters that can be accessed bythe user and/or clinician that are not shown in the figure. For example,the charge state of the battery can be indicated to the user through theuser display 714. The integrity of the electrodes may be monitored bythe implanted system, and their status can be displayed to the user ifnecessary. Other information, such as the direct sensor outputs, can beobtained by a clinician or researcher as needed.

It will also be noted that control of the system may be distributedamong various processes which may be located in a central controller atthe bridge, or at modules distributed throughout the system. Thus in oneaspect there is disclosed herein a distributed controller for use in aneural prosthesis.

It will be appreciated that the systems described herein may be adaptedto a variety of neural prosthetic applications using the modules 104,communication medium 102, and bridge 400 described above. Thus theapplication of the invention is not limited to the specific examplesabove, nor is the application of the invention limited to motorneuroprosthetics. The following examples show other potentialapplications of the system.

Hand Function System.

A C7 level spinal cord injury results in the loss of finger and thumbflexion. Electrical stimulation can be used to activate these paralyzedmuscles to provide grasp and pinch force. Control of the stimulation ofthese muscles can be provided by activity of the wrist extensors, whichare under voluntary control. Wrist extensor activity can be detected byrecording the electro-myographic (EMG) signal. This can be implementedusing the systems described above. A stimulator module may be placed tostimulate the finger and thumb flexors. An EMG electrode may beimplanted on the extensor carpi radialis brevis (ECRB), and an EMGsignal processing module may also placed in the forearm. These two unitsare networked. The recorded EMG signal may be converted into a signaland used to determine the user's desired stimulus levels for the sixelectrodes. Functionally, the user will find that as he extends hiswrist, his hand will close, and he can open his hand by voluntaryflexing his wrist and/or voluntarily extending his fingers and thumb.

Whole Arm Function System.

Complete loss of arm function results from spinal cord injury at the C4(or higher) level. Restoring function for these individuals requiresstimulation of hand, arm and shoulder muscles in a coordinated fashion.User control of arm function is obtained by utilizing voluntarymovements generated by the user's head and neck. Using the neuralprosthetics described above, electrodes may be placed in the hand,forearm, arm, and chest. Sensor modules can be located in these regionsof the body. Three muscle-based actuator modules and three nerve basedactuator modules are used to stimulate 26 different muscles. Voluntarycontrol is achieved by recording EMG from the frontalis,sterno-cleido-mastoid and trapezius muscles. Electro-oculogram (EOG)signals can also be recorded from the electrodes placed on the frontalismuscle, allowing eye movements to be used as an additional controlinput. Orientation sensors may be placed on the ulna, humerus andsternum, and provide feedback information regarding the position of thearm in space. Each module may be connected through the network to thebridge. The bridge may provide additional processing power for EMGsignal acquisition and/or interpretation. This system may provide theuser with hand and arm function.

Standing, Walking and Bladder/Bowel Function System.

Spinal cord injury at the C8 through T12 level results in completeparalysis of the lower extremities, as well as loss of bowel, bladderand sexual function. Research has demonstrated that each of thesefunctions can be restored using electrical stimulation. The systemsdescribed herein may be used to realize restoration of all of thesefunctions with a single neural prosthesis. A total of 12 muscle-based ornerve-based electrodes may be used for each hip and knee flexion andextension, hip adduction and abduction, ankle plantar and dorsi-flexion,and extension. Three actuator modules with nerve cuff electrodes areplaced on the S1, S2 and S3 dorsal roots to provide bladder, bowel andsexual function. Sensor modules with accelerometers may be placed on thehip, femur and tibia, and used to obtain information about leg position.Sensor modules with contact sensors may be placed in the sole of thefoot to record floor impact. A bridge may provide centralized power tothe system of networked modules. Processing capacity may be deployedwithin modules in the legs and/or provided centrally at the bridge. Thissystem may restore an individual's ability to stand and take steps, andmay concurrently be applied to restore bladder function, bowel function,and sexual function.

Hemiplegia Walking System.

Hemiplegia can result from a stroke or incomplete spinal cord injury.Sensor modules placed in the normal leg can be used to control theelectrical stimulation of the paralyzed leg to produce coordinatedmovements such as standing and walking. Sensor modules having EMGelectrodes may be placed in the non-paralyzed leg to detect activity inthe hip and knee muscles. Sensor modules that detect contact may beplaced in both feet to identify specific stages of the gait cycle. Inthis system, signal processing may be performed at one or more of thesensor modules to provide real-time control of the affected limb.

Other Applications.

The invention allows general input and output devices to be connected toa very flexible network providing communication and power. Therefore,various types of mechanical actuators, such as drug delivery pumps,could be included in this system. Chemical sensors can be incorporatedinto this system, for example providing devices that could sense thelevel of a particular drug or other circulating metabolic compound anduse that signal to control the level of drug delivery through aminiature implanted pump. Other neural prosthetic systems, such asvisual or cochlear prostheses would benefit from the existence of neuralprosthesis capable of stimulation through various types of electrodes;and sensor modules. The clinical potential of the systems describedherein is quite broad, extending well beyond neurological injuries.

Thus, having shown the preferred embodiments, one skilled in the artwill realize that many variations are possible within the scope andspirit of the claimed invention. It is therefore the intention to limitthe invention only by the scope of the following claims.

What is claimed is:
 1. A method for controlling a paralyzed region of abody, the method comprising the steps of: implanting a neural prosthesisin the body, the neural prosthesis comprising: at least two modules,each module comprises an actuator and a housing that encloses a networkinterface and a processor, wherein the at least two modules communicatewith each other via a network link; and a power source linked to each ofthe at least two modules to provide a power signal to each of themodules via the network link; detecting, by at least one of the modules,at least one input signal; and applying an output signal, by the atleast one of the modules in response to the at least one input signal,to a portion of the nervous system to initiate a body functionassociated with the paralyzed region.
 2. The method of claim 1, whereineach of the modules receives all operational power remotely.
 3. Themethod of claim 1, wherein at least one of the modules is implantedwithin a paralyzed extremity.
 4. The method of claim 1, wherein at leastone of the modules is implanted in a non-paralyzed extremity.
 5. Themethod of claim 1, wherein the input signal is one of an EEG signal, anEMG signal, an EOG signal, a signal derived from a three-dimensionalaccelerometer, a signal derived from a nerve recording, or a signalassociated with a physiological quantity.
 6. The method of claim 1,wherein the stimulus delivered by the output signal is caused bydelivery of a drive pulse or a drug.
 7. The method of claim 1, whereineach module transmits and receives signals across the network link at asame fundamental data rate.
 8. The method of claim 7, wherein thefundamental data rate is based on a frequency of alternating pulses fromthe power source.
 9. The method of claim 1, wherein the network linkcomprises a wired connection.
 10. The method of claim 1, wherein eachmodule communicates across the network link at the same time.
 11. Themethod of claim 10, wherein each module communicates across the networklink according to a controller area network (CAN) protocol.
 12. Themethod of claim 1, wherein each module further comprises a sensorconfigured to receive the at least one input signal transmitted via thenetwork link.
 13. A method for controlling first and second paralyzedregions of a body, the method comprising the steps of: implanting aneural prosthesis in the body, the neural prosthesis comprising: a firstmodule implanted in the first paralyzed region and a second moduleimplanted in the second region, each module comprises an actuator and ahousing that encloses a network interface and a processor, wherein theat least two modules communicate with each other via a network link; anda power source linked to each of the at least two modules to provide apower signal to each of the modules via the network link; detecting, bythe first module or the second module, a plurality of input signals; andapplying, by the first module or the second module in response to theplurality of input signals, output signals to stimulate a portion of thenervous system in the first region or the second region to initiate abody.
 14. The method of claim 13, wherein each of the modules receivespower remotely.
 15. The method of claim 13, wherein the first module andthe second module operate autonomously.
 16. The method of claim 13,wherein each module communicates across the network link at the sametime according to a controller area network (CAN) protocol.
 17. Themethod of claim 13, wherein the network link comprises a wiredconnection.
 18. The method of claim 13, wherein each module transmitsand receives signals across the network link at a same fundamental datarate based on a frequency of alternating pulses from the power source.19. A neural prosthesis system that controls a paralyzed region of abody, comprising: a first module comprising a first actuator and a firsthousing that encloses a first network interface to a network link and afirst processor; a second module comprising a second actuator and asecond housing that encloses a second network interface to the networklink and a second processor, wherein the first module and the secondmodule communicate with each other via the network link; and a powersource that provides a power signal to the first module and the secondmodule via the network link; wherein the first module and the secondmodule transmit and receive signals across the network link at a samefundamental data rate based on a frequency of alternating pulses fromthe power source.
 20. The neural prosthesis system of claim 19, whereinthe network link comprises a wired connection.